1. Technical Field
The present disclosure relates to a semiconductor integrated circuit and, more particularly, to a reference voltage generator for improving setup voltage characteristics without an increase in a standby current.
2. Discussion of Related Art
A reference voltage is generally used to determine a logic level of data. More specifically, data lower than the reference voltage is determined as a logic low level, and data higher than the reference voltage is determined as a logic high level. Thus, if a reference voltage level varies, a data logic level may be erroneously determined. In addition, the reference voltage can be used to generate an internal power voltage in a memory device, such as DRAM.
The reference voltage should always have a constant value even in the face of variations of a process, a temperature, and a power supply voltage. A circuit for generating the reference voltage must have good setup voltage characteristics. A variety of types of circuits are used to generate the reference voltage, and one example of a reference voltage generator is disclosed in U.S. Pat. No. 5,309,083 A.
FIG. 1 is a circuit diagram of a conventional reference voltage generator. FIG. 2 is a plot of voltages illustrating characteristics of the conventional reference voltage generator.
Referring to FIG. 1, the conventional reference voltage generator includes a voltage divider 11 that divides a power supply voltage VDD and outputs a reference voltage VREF to an output device, and a reference voltage controller 13 that controls the level of the reference voltage VREF in response to the control voltage VCON generated from the voltage divider 11.
The voltage divider 11 includes two resistors RS and R and two NMOS transistors N1 and N2. The reference voltage controller 13 includes a PMOS transistor P1.
The conventional reference voltage generator, however, determines a setup voltage VSET of the reference voltage VREF according to the resistor RS. In more detail, the smaller the value of the resistor RS becomes, the lower the setup voltage VSET becomes, resulting in the improvement of the setup voltage characteristics but causing an increase in a standby current.